This invention relates generally to a roller or caster assemblies, and more particularly to such assemblies including height-adjustable rollers particularly adapted for use with heavy household appliances, such as refrigerators and food freezers.
While refrigerators and food freezers are generally located in a portion of the house where the floors are relatively level, it is still necessary to provide a leveling device at each of the front edges of the appliance to ensure precise leveling and ensure that the doors will properly open and close. In their simplest form, such leveling devices may be adjustable legs that make a threaded engagement with a nut on the refrigerator and have a flat pad for engaging the floor. While such devices enable a refrigerator to be leveled, they make it difficult to move when it is desired to clean either the floor beneath the refrigerator, the wall behind it, or, in some cases, condenser coils that may be mounted along the rear wall of the refrigerator.
To allow easy movement of a refrigerator, it has been proposed to provide rollers at each of the front corners of the refrigerator and, optionally for easier movement, rollers at each of the rear corners. While the rear rollers may be fixed in place, the front rollers must be vertically adjustable for leveling purposes. Furthermore, adjustable height front rollers may also be used in combination with threaded adjustable legs where the friction provided by such legs is desirable to prevent movement when the refrigerator is in place. In such case, the adjustable rollers may be retracted when the refrigerator is in place, and then adjusted downwardly to lift the refrigerator off the threaded legs to allow movement. After the refrigerator is back in place, they can be retracted to permit proper positioning on the preadjusted threaded legs.
Roller arrangements that have been used heretofore may perform adequately when the refrigerator is in place in the home, but from the manufacturing point of view may suffer such shortcomings as high cost of manufacture and labor-intensive installation. Some versions also may require assembly prior to the finished assembly of the appliance, and therefore cannot be used as a dealer-installed option.
Other problems that occur with some of the prior art devices are difficulty of adjustment in the home, as well as the use of sliding surfaces which may suffer from greatly increased friction as the result of an accumulation of dust and dirt.
One example of such a structure is shown in U.S. Letters Patent to W. R. Cobb U.S. Pat. No. 3,437,346, granted Apr. 8, 1969, which shows a rear roller structure in which the roller is mounted on a pin inserted in bent-up tabs on the refrigerator bottom, while the front adjustable roller consists of a roller carrier mounted on vertical flanges on a frame fastened to the refrigerator and a vertically extending screw moves the roller carrier vertically for purposes of adjustment.
U.S. patent to K. K. Kesling et al. U.S. Pat. No. 3,534,430, granted Oct. 20, 1970, shows a fixed roller mounted in the housing attached to the bottom side of the side rails at the rear of the refrigerator and a rocking-type front roller mounted on a roller carrier in the form of a bell crank pivoted at one end to a housing attached at the bottom of the refrigerator while the upper end is moved by a threaded bolt arrangement having a long extension to the front of the refrigerator.
U.S. patent of John X. Matsykella et al. U.S. Pat. No. 3,844,578, granted Oct. 29, 1974, uses a vertically extending screw fixed in the refrigerator frame with a head projecting below the lower surface to receive a wrench for rotating the screw. The roller is mounted on a carrier, which makes threaded engagement with the screw while having projecting arms engaging the frame to prevent rotation of the roller frame.
U.S. patent to William P. Crowe U.S. Pat. No. 3,858,270, granted Jan. 7, 1975, requires the frame of the refrigerator to have a cross rail with a vertical surface joined at its upper end to a horizontal surface into which is threaded a vertical adjustment screw. Bolts hold a guide to the rear of the vertical surface to provide ways on which a rollersupport can be guided, while the support at its end engages the adjusting screw so that rotation of the adjusting screw moves the roller support vertically with respect to the frame cross member.